This invention relates to vehicle powertrains, and more particularly, to powertrains having an engine, torque converter, a transmission and a coupling between the engine and torque converter.
Specifically, this invention relates to powertrain systems, wherein the coupling between the engine and torque converter is divided into two inertia mass components, one connected with the engine and the other connected with the cover and impeller of the torque converter, and also wherein a spring and friction isolator assembly is disposed to transmit power between the inertia masses while damping torsional vibrations.
Many of the current automotive automatic transmissions employ a selectively engageable friction clutch and isolator assembly to connect the torque converter impeller and torque converter turbine together thereby improving driveline efficiency. With these systems, clutch engagement at low engine speeds generally results in driveline disturbances which are perceived by the driver and therefore limit the engagement speed range.
In an attempt to lower the engine speed at which the clutch can be engaged without these disturbances occurring, some transmissions utilize a viscous slipping clutch disposed in series with the friction clutch. While this arrangement does permit lower engagement speeds, the cost of the system increases and some efficiency loss remains.
Dual mass flywheel systems have been proposed to reduce driveline disturbances in countershaft type transmissions with synchronizer shifting controls. In these powertrain systems, the engine and transmission are completely disconnected during ratio interchanges by a selectively engageable clutch member. While these systems do provide some improved driveline damping, they include an increased number of spring systems and/or friction interface connections to release the inertia load from the synchronizers during a ratio interchange. These systems can be very complex and more costly than conventional powertrains.